Trajectory simulator



March 22, 1960 R. B. REDDY TRAJECTORY SIMULATOR 2 Sheets-Sheet 1 Filed March 10, 1953 FIG. I.

INVENTOR ROBERT B. REDDY Q a m? March 22, 19 60 R. B. REDDY 2,929,156

TRAJECTORY SIMULATOR Filed March 10, 1953 2 Sheets-Sheet 2 as 2 FIG. 3.

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INVENTOR i ROBERT a. nanny 140.49% /8 22 I9 22 BY Q ATTORNEYS United States Patent 1 2,929,] 56 TRAJECTORY SIMULATOR Robert B. Reddy, Annapolis, Md., assignor to the United States of America as represented by the Secretary of the Navy Application March 10, 1953, Serial No. 341,405 3 Claims. (Cl. 3510.4)

This invention relates generally to simulators, and more particularly to trajectory simulators to be used in the analysis of radar beam program systems and of their effects upon the trajectories of guided aerial missiles.

In one type of guidance system for aerial missiles, the missile is made to follow a radar beam, the movement of which is programmed in such a manner that the missile is caused to fly an up and over trajectory, i.e. to climb to a specified altitude and then proceed substantially horizontally to meet an intended target. An up and over trajectory is particularly advantageous from a propulsion standpoint in that the propulsion requirements in level flight are much less stringent than those imposed upon the missile during a sustained climbing flight.

In order that the missile may fly an up and over trajectory and still meet the target at some future time, the radar beam must be properly programmed. Furthermore, for different missile launching angles and for various target situations the radar beam must be programmed differently. In selecting the proper beam program for a particular missile launching angle and target situation, it is necessary to determine the effect of several beam programs on the trajectory of a missile. Inasmuch as an infinite number of possible programs are available, but only one will properly serve the purpose of guiding a missile in an up and over trajectory to its intended target, a rapid and easy means of determining the effects of several beam programs on the missile trajectory is desirable.

The problem of selecting a proper beam program then resolves itself into a prediction of the trajectory of a missile flying under the influence of a given beam program. For practical purposes in solving this problem, the maneuver of the missile in azimuth may be neglected, so that the problem is reduced. from a three dimensional type to a two dimensional one.

At first, the solution of a mathematical representation of the trajectory would appear to be the quickest, simplest, and most accurate method of investigating beam programs. However, the mathematical equation representing the trajectory cannot be solved in closed form, even through it is of first order. Furthermore, a series solution of the equation proves to diverge as often as not. Therefore, the mathematical solution of the mathematical representation of the trajectory is not possible.

It is possible to solve the mathematical equation with suflicient accuracy by means of a variation of the stepby-step procedure as commonly used in trajectory work. However, if a large number of programs are to be investigated, the labor and time involved are prohibitive.

The principal object of the present invention is to provide a device wherein the trajectory of a missile operating under the influence of a given radar beam program may be simulated upon a sheet of graph paper or like recording surface.

It is a further object of the invention to provide a device which permits the analysis of the effects of a radar beam program on a missile trajectory by simulating a radar beam or the like for guiding missiles and a missile guided by the beam.

Further objects and advantages will become apparent from the following detailed description of a preferred em bodiment of the invention, as illustrated in the accompanying drawings, in which:

- being defined by a spaced bracket 26a.

2,929,156 Patented Mar. 22, 1960 Fig. 1 is a diagrammatic view showing the simulator in consecutive positions of a simulated missile flight, thus illustrating the operation of the device;

Fig. 2 is a side elevation, partially broken away, of a preferred embodiment of the invention;

F Fig. 3 is a section of the simulator, on line 22 of Fig. 4 is a fragmentary plan view of the simulator shown in Fig. 2;

Fig. 5 is a fragmentary sectional view similar to that shown in Fig. 3, illustrating a modified form of marking means employed by the simulator; and

Fig. 6 is a plan view of a modified form of the simulator, portions of which are shown fragmentarily.

Generally, the invention consists of a pivoted member simulating the radar beam along which the missile is constrained to fly, and an inscribing member simulating the missile itself. The inscribing member is constrained to move along the pivoted member at a constant rate relative to the recording surface while at the same time inscribing its path of travel over the recording surface. The pivoted member is made to pivot at a variable rate consonant with the given radar beam system. Thus, a simulated trajectory is simply, quickly and accurately described.

A simulator embodying the invention is shown in Fig. 1, and, in general, includes a rail 11 pivotally mounted at a point P on a recording surface S and a carriage 12 movably supported on said surface and constrained to movement along said rail.

For a more detailed description of the invention reference is had to Figs. 2, 3, 4 and 5, wherein the rail 11 is shown as being of I-beam construction having substantially V-shaped grooves 13 cut longitudinally into the under side of its upper flanges. The rail 11 is pivotally supported at one end by a pivot pin 14 and movably supported at its other end by a caster 15 which moves over the suitable recording surface S.

A direction controller apparatus 16, of the type used to direct guidance radar transmitters in programming radar beams for guiding actual missiles in flight, has an output shaft 17 drivably connected to the pivot pin 14. A con troller of this type receives angular and range information concerning a particular target situation from a tracking radar and the launcher mechanism and operates upon said information in a specified manner to program the guidance radar beam so that a missile flying the beam will proceed in an up and over trajectory to meet the target.

The carriage 12, to be more fully described hereinafter, is swivelly connected to a yoke 18 having legs 19 which straddle the lower portions of the rail 11. Pairs of guide rollers 21 are rotatably mounted on axles 22 mounted on each of the projecting legs 19 of the yoke 18, so that one pair of said rollers is disposed in each channel of the rail 11. The peripheries 23 of the rollers 21 are tapered to fit into and be guided by the V-shaped grooves 13 in which they move, thus constraining the yoke 18 to movement along the rail 11.

The carriage 12 includes a flat base or platform 24 having a depending stylus holder 24a, to be more fully described hereinafter. One end portion of the platform is bent downwardly through degrees to define a leg 26 of a wheel mounting 25, the other leg of said mounting The mounting 25 journals a drive shaft 27 which extends under the platform 24, said shaft having a drive wheel 28 secured thereon. A caster 29 is also mounted on the under side of the carriage 12 at its opposite end and together with the drive wheel 28, supports the carriage for movement on the recording surface S. In order to provide good traction for the drive wheel 28 on the surface S, the peripheral surface of said wheel is preferably provided with a rubber tire 31.

A bevel gear 32 is fitted on the inner end of the drive shaft 27 and a synchronous motor 33 is riveted or otherwise secured to the upper surface of platform 24. The motor 33 has an output shaft 34 extending through a suitable opening in the platform and carries a bevel gear 35 at its free end. The bevel gear 35 on the output shaft 34 meshes with the bevel gear 32 on the drive shaft 27, to transmit rotative motion from the motor 33 to the drive wheel 28. In this manner the carriage 12 is propelled over the the recording surface S.

The synchronous motor 33 is energized by electrical power supplied from a suitable source through a flexible cable 36. However, electrical power may be conducted to the motor in any of a number of different ways.

The stylus holder 24a terminates in an end portion 37 which is substantially parallel to said platform. The end portion 37 is suitably apertured to mount a stylus or pen assembly 38 which bears on the recording surface S, to make appropriate markings thereon. Because the path of movement of the drive wheel 28 most closely simulates the path of the missile, the end portion 37 and pen assembly 38 are disposed as near to said wheel 28 as possible without interferring with the functioning of said wheel.

An ideal arrangement would have the marking means incorporated as a part of the drive wheel itself, as for instance a wheel operating on the same principle as an inking roll commonly found in mimeograph machines. A wheel 39 of this type is shown in Fig. as being constructed with rubber tires 41 on the outer portions of its peripheral surface and with a band 42 of felt or other absorbent material on the intermediate portion of said peripheral surface. In this modification of the marking means, an ink reservoir 43 is mounted on the platform 24 and supplies ink through a conduit 44 to the band 42.

The operation of the simulator, hereinafter described in detail, will be better understood with additional reference to Fig. 1, wherein the instant location of the rail 11 and the carriage 12 is shown in solid lines and prior and subsequent locations of said rail and carriage, as the rail is pivoted about a pivot point P which is generally indicative of the position of the pivot pin 14, are shown in broken lines. The instant location of the rail is generally designated as C while the successive preceding locations of the rail are respectively designated as A and B, and the successively subsequent locations are respectively designated as D and E.

In its initial location A, the rail 11 simulates the angle at which the missile is to be launched. When the rail is in this location, the carriage 12 is in close proximity to the pivot pin 14 which represents the launching site. To commence the operation of the simulator, the controller apparatus 16 is activated to drive the pivot pin 14 at a variable rate corresponding to the beam program under investigation, thereby pivoting the rail 11 about the pivot point P. Simultaneously, with the activation of the controller apparatus 16, the synchronous motor 33 is energized to rotate the output shaft 34 at a constant rate. The output shaft 34 transmits rotative motion through the bevel gears 35 and 32 to the drive shaft 27 which, in turn, drives the drive wheel 28 to propel the carriage 12 over the recording surface S at a constant rate relative to said surface and representative of the missile velocity. It is to be noted that inasmuch as the carriage 12 is pivotally attached to the yoke 18, which in turn is constrained to movement along the rail 11, the direction but not the rate of movement of said carriage is controlled by the movement of said rail. As the rail 11 pivots about the pivot point P from location A through location B to location C and as the carriage 12 moves out from the point P, the pen assembly 38 bears on the recording surface S to leave a trace T which is a simulation of the missile trajectory.

The solid trace T is the trajectory traveled by the carriage 12 from its initial location A to the full-line location C, while a broken trace T represents the trajectory said carriage will travel under the beam program being investigated.

Other methods of pivoting the rail 11 about the pivot point P at a variable rate consonant with a given beam program may be employed. As an example, reference is had to Fig. 6, wherein there is shown a modified rail 35, similar in all respects to the rail described in connection with Figs. 1, 2 and 3 except that said modified rail includes an extended portion 46, to the under side of which is mounted a pin 47. The modified rail 45 is pivotally supported at point P on a recording surface S. A template 48 having a cam surface 49 which engages the pin 47 is adapted to move linearly to the left as indicated in Fig. 6 at a constant rate. The cam surface 49 corresponds to a given beam program so that as the template 48 moves to the left said cam surface moves the pin 47 to pivot the rail 45 at a variable rate consonant with the given beam program.

To investigate a diiferent beam program the template 48 may merely be replaced by a template having a different cam surface which is representative of a new beam program. Any number of beam programs may be investigated simply by employing a number of templates having cam surfaces corresponding to those beam programs.

Obviously many modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

What is claimed is:

1. A device for simulating the constant velocity trajectory of a missile under the guidance of a radar beam program, comprising, a recording surface having a rectangular system of coordinates indicated thereon, an arm mounted on said recording surface and constrained to pivot about the origin of said system of coordinates and in a plane parallel to said surface, means coupled to said arm for pivoting said arm at a variable rate in consonance with said radar beam program, said means being responsive to information corresponding to that supplied by said radar beam program, a member slidably mounted on said arm for longitudinal movement thereon, driving means for propelling said member over said surface at a constant rate, and marking means on said member for continuously inscribing upon said surface the position of said member as said member moves over said surface and longitudinally on said arm simultaneously as said arm pivots at said variable rate.

2. The apparatus recited in claim 1 wherein said means for pivoting said arm includes a direction controller of the type used to direct guidance radar transmitters in programming radar beams for guiding actual missiles in flight.

3. The apparatus recited in claim 1 wherein said means for pivoting said arm includes a plurality of interchangeable templates each having a different cam surface thereon, each of said cam surfaces corresponding to a possible trajectory of said radar beam program and engageable with said arm, whereby certain movement of one of said templates causes said arm to engage the cam surface of said one template to pivot said arm at a variable rate in consonance with the trajectory represented on said one template.

References Cited in the file of this patent UNITED STATES PATENTS 1,782,294 Florisson Nov. 18, 1930 1,844,905 Schweydar Feb. 9, 1932 2,437,243 Curtis Mar. 9, 1948 FOREIGN PATENTS 384,971 Great Britain of 1931 

